From a02553815f9eac0a3b0763fb0cea62a44b030373 Mon Sep 17 00:00:00 2001
From: Preston Van Loon <preston@prysmaticlabs.com>
Date: Tue, 7 Jul 2020 22:47:26 -0700
Subject: [PATCH] Allocate the appropriate memory for
 retrieveIndicesFromBitfield (#6507)

* Allocate the appropriate memory for retrieveIndicesFromBitfield
* Merge refs/heads/master into memory0
* Merge refs/heads/master into memory0
* Merge refs/heads/master into memory0
* Merge refs/heads/master into memory0
* Merge refs/heads/master into memory0
* Merge refs/heads/master into memory0
* Merge refs/heads/master into memory0
---
 beacon-chain/p2p/peers/BUILD.bazel       |  5 ++++-
 beacon-chain/p2p/peers/benchmark_test.go | 18 ++++++++++++++++++
 beacon-chain/p2p/peers/status.go         |  2 +-
 3 files changed, 23 insertions(+), 2 deletions(-)
 create mode 100644 beacon-chain/p2p/peers/benchmark_test.go

diff --git a/beacon-chain/p2p/peers/BUILD.bazel b/beacon-chain/p2p/peers/BUILD.bazel
index c8be51b367..055366c448 100644
--- a/beacon-chain/p2p/peers/BUILD.bazel
+++ b/beacon-chain/p2p/peers/BUILD.bazel
@@ -22,7 +22,10 @@ go_library(
 
 go_test(
     name = "go_default_test",
-    srcs = ["status_test.go"],
+    srcs = [
+        "benchmark_test.go",
+        "status_test.go",
+    ],
     embed = [":go_default_library"],
     deps = [
         "//proto/beacon/p2p/v1:go_default_library",
diff --git a/beacon-chain/p2p/peers/benchmark_test.go b/beacon-chain/p2p/peers/benchmark_test.go
new file mode 100644
index 0000000000..7c72ef02e2
--- /dev/null
+++ b/beacon-chain/p2p/peers/benchmark_test.go
@@ -0,0 +1,18 @@
+package peers
+
+import (
+	"testing"
+
+	"github.com/prysmaticlabs/go-bitfield"
+)
+
+func Benchmark_retrieveIndicesFromBitfield(b *testing.B) {
+	bv := bitfield.NewBitvector64()
+	for i := uint64(0); i < bv.Len(); i++ {
+		bv.SetBitAt(i, true)
+	}
+	b.ResetTimer()
+	for i := 0; i < b.N; i++ {
+		retrieveIndicesFromBitfield(bv)
+	}
+}
diff --git a/beacon-chain/p2p/peers/status.go b/beacon-chain/p2p/peers/status.go
index 415bcb56c5..2a62757764 100644
--- a/beacon-chain/p2p/peers/status.go
+++ b/beacon-chain/p2p/peers/status.go
@@ -493,7 +493,7 @@ func (p *Status) HighestEpoch() uint64 {
 }
 
 func retrieveIndicesFromBitfield(bitV bitfield.Bitvector64) []uint64 {
-	committeeIdxs := []uint64{}
+	committeeIdxs := make([]uint64, 0, bitV.Count())
 	for i := uint64(0); i < 64; i++ {
 		if bitV.BitAt(i) {
 			committeeIdxs = append(committeeIdxs, i)